From a viewpoint of energy conservation, an automobile is required to increase gas mileage, and an electric automobile driven by a motor and a hybrid car driven by a combination of a motor and an engine now receive attention. A high-capacity, on-vehicle motor used in an automobile is difficult to drive and control by using a DC voltage from a battery, and an electric power converter that uses switching operation of a power semiconductor device is essentially required for voltage step up and AC control. Since a power semiconductor device generates heat when energized, a power semiconductor module having a power semiconductor device incorporated therein requires an insulation layer having a high heat dissipation capability.
For example, a known power semiconductor module of this type has a structure in which a power semiconductor device and a conductor plate on which the power semiconductor device is mounted are sealed with a resin to form an integrated structure and a ceramic insulation layer is formed on the lower surfaces of the conductor portion and the resin portion in a spray coating process (see PTL 1, for example). Since a ceramic insulation layer has excellent thermal conductivity, the ceramic insulation layer with a heat sink for cooling purposes layered thereon allows a power semiconductor module having an excellent heat dissipation characteristic to be manufactured at low cost.